A microrobot to explore the blood vessels of the brain

A microscopic robot that moves in the smallest blood vessels to access the circulatory system of the brain and deliver drugs against neurological diseases. In the group of scientists of the Federal Polytechnic of Lausanne (EPFL), coordinated by Prof. Mahmut Selman Sakar, also the Swiss-Italian researcher Lucio Pancaldi.

Finding advanced technological solutions able of opening new frontiers in scientific exploration is the basis of the study of the first explorer micro robot capable of traveling inside the peripheral arteries. The study was published in the journal "Nature Communications".

"As an academic group we seek to develop new methods that make use of phenomena present at microscopic scales to develop technologies capable of answering currently open scientific questions." Lucio Pancaldi, an Italian Swiss researcher in the last year of his doctorate at the MicroBioRobotic Systems(MICROBS ) of ECOLE POLYTECNIQUE FEDERALE DE LOSANNE ( EPFL), and co-author in the study regarding a micro robot able to move inside microscopic vessels to release drugs against neurological diseases or during minimal invasive surgeries.

Lucio Pancaldi

“This publication stems from the fact that, although minimally invasive medical procedures have significantly reduced procedure times, many regions within the body, such as the cerebral vascular system, are currently still unexplored due to the lack of adequate guidance technologies. Our goal was to find a minimally invasive navigation method compatible with miniaturizing electronic endovascular probes in order to access any artery in our body ".

Classic catheters are pushed by the surgeon and directed using the so-called "guidewires", or guides: thin metal wires inserted coaxially into the catheters that help navigation of the latter. The classical systems, however, suffer from a compromise that precludes their miniaturization, and therefore the possibility of pushing navigation towards the smallest and most remote peripheral vessels. Basically, the guides and the catheters must be flexible enough to be able to be navigated through the tortuosity of the cerebral vessels without causing damage, but at the same time rigid enough to support the compression given by the thrust force applied by the surgeon. It is therefore easy to imagine that guides that are too miniaturized, therefore too flexible, fail to transmit the thrust towards the tip and therefore collapse inside the arteries. "The reasoning behind our navigation method was therefore to drastically and further decrease the thickness of our probes, to such an extent that the extreme flexibility ensures that the probes can be transported and directed by the fluid itself. In this way we pass from a state of compression (like catheters) to a regime of tension constantly ensured by the blood flow ”. The microscopic probes developed by the Lausanne researchers are made of an ultra-flexible body of biocompatible polymer and can reach sizes smaller than those of a human hair. To increase driving skills, a magnetic compound is added to the distal end.

Illustrative representation of the main features and advantages of endovascular microprobes

 “in case we need to change the way in the presence of a bifurcation (if simply released, the probes will follow the most predominant fluid path), we activate computerized electromagnets that impose a rotation of the tip in the direction of the magnetic field. In this way, we can operate the probes with a simple joystick ”. Since the contact points are reduced to the inner walls in curves and no substantial mechanical forces are applied during navigation, the risk of causing damage is very low. "With the help of a mathematical model, we have estimated that the compressive forces on the arterial walls are more than a thousand times lower than the forces exerted by classic catheters. While the numbers are encouraging, it remains extremely difficult to measure these kinds of forces in representative models. Future histological examinations will confirm the validity of the model ". In addition to the reported decrease in contact forces, the exploitation of blood fluid as the primary source of propulsion leads to a number of additional benefits. For example, the almost total supervision of the fluid in autonomously transporting the probes through complicated passages, such as stenoses, allows to reach navigation speeds that approach the speed of the fluid itself. This would one day allow interventional radiologists to reach the injured party with unprecedented speed. “We aim to reach destinations in just a few minutes, this would allow us to act extremely quickly in cases where every minute counts”. The autonomous capabilities of the microprobes in circumventing obstacles should also allow the navigation process to be robotized in the future. “In addition to the reduced possibilities of perforating the arteries, we can now think of developing fully autonomous robotic systems without danger to the patient”.

“Our technology is not intended to replace conventional catheters, but to increase their effectiveness ,” Pancaldi said. An innovative and revolutionary micro robotics tool able to help doctors treat neurological disorders or brain tumors in areas previously inaccessible. The first animal experimentation tests carried out within the ex vivo vascular system of a rabbit's ear have obtained encouraging results, the next step will be to conduct in vivo tests.

Video (Source: EPFL): https://www.youtube.com/watch?v=9Gov9TDsGEY&t=19s

*image: Magnetically guided endovascular microprobe with integrated electronic fluid sensor

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